1. Field of the Invention
The present invention relates to a photo-curable composition and a photo-cured product thereof (hereinafter, also called cured product or cured film). Specifically, the present invention relates to a photo-curable composition which is excellent in storage stability and applicable to the surfaces of plastics, metals, ceramics, glass, wood, papers and the like having various shapes and which can give a photo-cured product excellent in weather-ability, heat resistance, transparency and scratch resistance, as well as a photo-cured product thereof.
Accordingly, the photo-curable composition and photo-cured product of the present invention are suitable for use in paints for metals, sizing agents for use in slate materials, hard coatings for plastic films, hard coatings for printing paper, stain-proof films for floor and wall tiles, hard coatings for optical lens, protective films for display elements, anti-reflective films, highly reflective films, selectively permeable films, fibrous coating reinforcing materials, resins for optical three-dimensional molding, optical lens, packaging compounds for semiconductors, insulating layers for semiconductors, adhesives for semiconductors, adhesives for optical products, printing plate materials, optical light-guide materials and optical switching materials.
2. Prior Art
As materials for forming the transparent cured film, thermosetting polysiloxane compositions are known and disclosed in Japanese Patent Application Laid-Open No. Sho 53-12952 and the like.
However, the cured films obtained from such thermosetting polysiloxane compositions, though being superior in weather-ability and scratch resistance, should be thermally treated at high temperatures for a long time, so there are problems that the productivity is low and the type of usable substrate is limited. Further, such thermosetting polysiloxane compositions have a problem that their performance becomes inferior during storage at normal temperatures, so they should be stored in a low-temperature state under the strict control of temperature.
On the other hand, as materials for forming the transparent cured film, photo-curable acrylic compositions which can be cured by using such rays as a UV light, are also known. Such photo-curable acrylic compositions are utilized in the field of hard coating and the like in various plastics because their curing rate is high and they can be cured at normal temperatures.
However, since the major components in the photo-curable compositions are an acrylic resin, there is a problem of low heat resistance and weather-ability as compared with the above-described thermosetting polysiloxane. In addition, since radical polymerization is utilized for the photo-curable acrylic compositions, there is a problem that inactivation of active radicals by oxygen in the atmosphere easily occurs so insufficient curing readily results. In particular, such insufficient curing easily occurs upon exposure to UV rays under the atmosphere.
Accordingly, photo-curable compositions having polymerizable groups such as a vinyl group, an epoxy group and the like introduced into silane compounds have been proposed for the purpose of improving weather-ability and scratch resistance. For example, U.S. Pat. No. 5,385,955 discloses a photo-curable composition comprising alkoxy silane having an epoxy group, a hydrolyzate of alkyl alkoxy silane, colloidal silica, and a photo-initiator.
However, there is a problem that such photo-curable compositions are sensitive to moisture while their photo-curing time (photo-curable property) is long. Accordingly, the insufficient curing easily occurs and there is a problem of unstableness in the characteristics of the resulting photo-cured products, such as heat resistance and weather-ability. On the other hand, if their photo-curable rate is raised, there is a problem that the storage stability of the photo-curable composition easily becomes poor.
Accordingly, Japanese Patent Application Laid-Open No. Hei 6-148895 discloses a photo-sensitive resin composition comprising: an alkali-soluble siloxane polymer obtained by hydrolysis in the presence of water and a catalyst and subsequent removal of the water and the catalyst by use of a hydrophobic organic solvent and a drying agent; a photo acid generator; and a solvent, and the hydroxyl group itself possessed by the siloxane polymer is utilized for photo-curable reaction.
However, when the hydrophobic organic solvent is merely used, water cannot be removed sufficiently from the photo-sensitive resin composition, and further the photo-sensitive resin composition does not contain a hydrating agent, so it is not possible to eliminate the influence of water or moisture from the outside or of water generated with time from the siloxane polymer.